You're right that kids aren't small adults, the physiology, the doses, the presentations all differ, and crucially you're treating the family, not just the child. Master the basics of growth and development (milestones by age) and the vaccination schedule, because those come up constantly and on exams. Learn the common childhood illnesses and how they present differently by age. On the human side communication is doubled, you must connect with both the child and the worried parents, and a frightened parent needs reassurance and clarity as much as the child needs treatment. Get comfortable examining a squirming, scared kid, often opportunistically and playfully rather than head-to-toe in order. Warmth and patience are your best clinical tools in peds. Win the child's trust and the exam gets ten times easier.